413 Request Entity Too Large, when sending mail about 4MB

[cic]

Hello there,

I am using open xchange app suite and I am trying to send an email at about 4MB.

My server runs with apache. PHP and httpd are configured well, to allow sending mails at about 128M.

How to check, why the error is occuring?

Thank you.

[Wolfgang Rosenauer]

PHP settings have nothing to do with OX. But in any case 4MB is far too low to create a problem. The defaults are higher.
What is the exact OX log error?